1. Field of the Invention
The invention relates to a trackball module structure adapted to an electronic device and, more particularly, to a trackball module structure in which a trackball device and a control chipset are integrated to be a single module.
2. Description of the Related Art
Generally, a trackball is disposed on an electronic device to move a cursor. Especially to a portable electronic device such as a personal digital assistant, the trackball may facilitate the operation of a user. As shown in FIG. 1, it is a schematic diagram showing a conventional trackball. A trackball device 70 is formed by a ball 71, four magnetic rollers 73 and a casing 72 covering them. Afterwards, the trackball device 70 is disposed on the motherboard 75 of the electronic device. The motherboard 75 has four Hall ICs 74 corresponding to the magnetic rollers 73.
Thus, when the user rolls the ball 71, the magnetic rollers 73 rotate along with the rotation of the ball 71. Then, the Hall ICs 74 sense the magnetism change of the magnetic rollers 73 to make the cursor move according to the calculation of the electronic device. Thus, the relationship of the magnetic rollers 73 and the Hall ICs 74 may determine the sensing precision of the trackball.
However, to facilitate the operation of the user, the trackball device 70 should be fixed at the casing of the electronic device (not shown). The Hall ICs 74 are welded on the motherboard 75. Since manufacturing tolerance and assembling tolerance may exist between the trackball device 70 and the casing, the casing and the motherboard 75 and the motherboard 75 and the Hall ICs 74, the tolerance is accumulated, and the tolerance between the magnetic rollers 73 and the Hall ICs 74 may be large and is hard to be controlled. This not only affects the precision of the trackball, but also may affect the sensing ability and the operation of the user.
In the conventional technology, a reed switch is used to replace the Hall IC to reduce the cost and improve the reliability. However, since the assembly mode of the reed switch and the trackball device is not changed, the problem that the tolerance accumulates still exists. Once the sensing ability is not good, even if the manufacturing cost is reduced, the reliability cannot be improved.